Sleep apnea is a chronic sleep disorder that happens when a person stops breathing during sleep. Sleep apnea is most commonly diagnosed in middle aged males. It is estimated that about one in 20 adults has been identified with sleep apnea, and is about 2 to 8 times more common among men than among women. Recent studies have shown that the prevalence of childhood sleep apnea is much higher than we expected. In addition, obesity, enlarged tonsil tissues, nasal septum deviation, alcohol intake, smoking and sedative use are related to a high risk for sleep apnea.
The standard diagnostic tools for sleep apnea are overnight polysomnogram and overnight oximetry. A well-known evaluation method of an apnea includes a minimum 10 second interval between breaths, or a hypopnea in which airflow decreases by 50 percent for 10 seconds. The evaluation process is time consuming and labor intensive. Moreover, qualified staff is unable to measure polysomnogram values accurately with a standardized evaluation procedure.
In prior art, a 2D ultrasonic sensing device is used for diagnosing airway obstruction. However, the 2D ultrasonic sensing device is limited by the relative position between cross-sectional surfaces and a respiratory tract, such that regions of the respiratory tract cannot be positioned accurately. Additionally, when different operators use the 2D ultrasonic sensing device to scan the same region of the respiratory tract at different time, it may produce different results from different positions and different sectioning angles.